In addition to the 2014 service notice regarding "fake" D800E cameras, Nikon issued an update today and also included the D610 and D4s to the list of "fraudulently modified" DSLRs:

Nikon has confirmed that fraudulently modified and imitation products have been received by Nikon Service Centres for repair.

It seems that these fraudulently modified and imitation products are in circulation via Internet auctions and the like. As the Nikon warranty does not apply to fraudulently modified or imitation products, Nikon will not inspect or repair such products. In addition, Nikon cannot be held responsible in any way regarding the use of fraudulently modified products. Please take all necessary precautions to ensure the authenticity of a product before purchasing it.

Examples of the fraudulently modified products that have been brought to Nikon Service Centres:

a) D800 cameras fraudulently modified to make them look like D800E cameras
These are D800 cameras with which the outer cover has been fraudulently replaced with a D800E cover. When the “overview” display option is enabled in full-frame playback mode, the name of the camera used to capture the image is displayed in the top right corner of the monitor, allowing users to confirm the true name of their camera. If "NIKON D800E" is displayed, your camera is an authentic D800E. If any other name is displayed, your camera is a fraudulent D800E.

b) D7100 cameras fraudulently modified to make them look like D610 cameras
These are D7100 cameras with which the name plate, and/or other identifying feature, has been fraudulently replaced with that of a D610. This can be checked using the same “overview” display option as described above. If "NIKON D610" is displayed, your camera is an authentic D610. If any other name is displayed, your camera is a fraudulent D610.

c) D4 cameras fraudulently modified to make them look like D4S cameras